Essential Knowledge 2.E.2

Timing and coordination of physiological events are regulated by multiple mechanisms.

In plants, physiological events involve interactions between environmental stimuli and internal molecular signals.

Examples:

• Phototropism, or the response to the presence of light
• Photoperiodism, or the response to change in length of the night, that results in flowering in long-day and short-day plants

In animals, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues.

Examples:

• Circadian rhythms, or the physiological cycle of about 24 hours that is present in all eukaryotes and persists even in the absence of external cues
• Diurnal/nocturnal and sleep/awake cycles
• Jet lag in humans
• Seasonal responses, such as hibernation, estivation and migration
• Release and reaction to pheromones
• Visual displays in the reproductive cycle

In fungi, protists and bacteria, internal and external signals regulate a variety of physiological responses that synchronize with environmental cycles and cues.

Examples:

• Fruiting body formation in fungi, slime molds and certain types of bacteria
• Quorum sensing in bacteria

Students should be able to:

LO 2.35 design a plan for collecting data to support the scientific claim that the timing and coordination of physiological events involve regulation.

LO 2.36 Justify scientific claims with evidence to show how timing and coordination of physiological events involve regulation.

LO 2.37 Connect concepts that describe mechanisms that regulate the timing and coordination of physiological events.